netdev - Re: [PATCH bpf-next v5 2/2] samples: bpf: refactor perf_event user program with libbpf bpf

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Message-ID: <CAEf4BzbTYyBG4=Muj5EOqtNxkivtT9Bn5+ibmp3e-BLBybQO1A@mail.gmail.com>
Date:   Sat, 21 Mar 2020 12:43:41 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     "Daniel T. Lee" <danieltimlee@...il.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v5 2/2] samples: bpf: refactor perf_event user
 program with libbpf bpf_link

On Sat, Mar 21, 2020 at 3:04 AM Daniel T. Lee <danieltimlee@...il.com> wrote:
>
> The bpf_program__attach of libbpf(using bpf_link) is much more intuitive
> than the previous method using ioctl.
>
> bpf_program__attach_perf_event manages the enable of perf_event and
> attach of BPF programs to it, so there's no neeed to do this
> directly with ioctl.
>
> In addition, bpf_link provides consistency in the use of API because it
> allows disable (detach, destroy) for multiple events to be treated as
> one bpf_link__destroy. Also, bpf_link__destroy manages the close() of
> perf_event fd.
>
> This commit refactors samples that attach the bpf program to perf_event
> by using libbbpf instead of ioctl. Also the bpf_load in the samples were
> removed and migrated to use libbbpf API.
>
> Signed-off-by: Daniel T. Lee <danieltimlee@...il.com>
>
> ---

LGTM.

Acked-by: Andrii Nakryiko <andriin@...com>

> Changes in v2:
>  - check memory allocation is successful
>  - clean up allocated memory on error
>
> Changes in v3:
>  - Improve pointer error check (IS_ERR())
>  - change to calloc for easier destroy of bpf_link
>  - remove perf_event fd list since bpf_link handles fd
>  - use newer bpf_object__{open/load} API instead of bpf_prog_load
>  - perf_event for _SC_NPROCESSORS_ONLN instead of _SC_NPROCESSORS_CONF
>  - find program with name explicitly instead of bpf_program__next
>  - unconditional bpf_link__destroy() on cleanup
>
> Changes in v4:
>  - bpf_link *, bpf_object * set NULL on init & err for easier destroy
>  - close bpf object with bpf_object__close()
>
> Changes in v5:
>  - on error, return error code with exit
>
>  samples/bpf/Makefile           |   4 +-
>  samples/bpf/sampleip_user.c    |  98 +++++++++++++++--------
>  samples/bpf/trace_event_user.c | 139 ++++++++++++++++++++++-----------
>  3 files changed, 159 insertions(+), 82 deletions(-)
>

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